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New stone formation: a comparison of extracorporeal shock wave lithotripsy and percutaneous nephrolithotomy
L K Carr1, J D'A Honey, M A Jewett
1Department of Surgery, University of Toronto, Ontario, Canada.
Purpose:
There is theoretical concern that stone recurrence rates may be higher following extracorporeal shock wave lithotripsy (ESWL) compared to other techniques because of residual stone debris.
Materials And Methods:
We documented all new stone formations in 298 consecutive patients who initially achieved a stone-free status following ESWL for renal calculi less that 2 cm in largest dimension, and compared the findings to those of 62 patients treated with percutaneous nephrolithotomy without ultrasonic fragmentation. Stone-free status was assessed by a centrally reviewed plain abdominal film and renal tomograms at 3 months. A plain abdominal film was repeated at 12 and 24 months to detect recurrence.
Results:
New stones formed in 22.2% of patients after ESWL and 4.2% after percutaneous nephrolithotomy at 1 year (p = 0.004), and in 34.8% versus 22.6%, respectively, at 2 years (p =0.190). Furthermore, more new stones recurred in the lower and mid calices compared to baseline location in the ESWL group (chi-square <0.0001), which was not observed in the percutaneous nephrolithotomy group.
Conclusions:
Our data support a trend toward higher stone recurrence rates in ESWL treated patients, which may be due to microscopic sand particles migrating to dependent calices and acting as a nidus for new stone formation.